Process of preparing fibrous pulp material



UNHTEB srares PATENT OFFHCEQ CARL BAGHE-WIIG AND JOHN BACHE-WIIG, OF PORTLAND, MAINE; SAID JOHN BACHE-WIIG ASSIGNOR 0F EIGHTY PER CENT OF HIS INTEREST TO SAID CARL BACHE-WIIG.

PROCESS OF PREPARING FIBROUS PULP MATERIAL.

No Drawing.

To all whom it may concern:

Be it known that we, CARL BAoHE-lVnc and JOHN BACHE-VIIG, both citizens of the United States, residing at Portland, in the county of Cumberland and State of Maine, have invented certain new and useful Improvements in Processes of Preparing Fibrous Pulp Material; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a process of preparing fibrous paper pulp material suitable for making print papers, from rye, wheat and other straws, and from similar fibrous cellulosic substances, and has for its objectto improve certain of the somewhat similar processes which have been heretofore proposed.

With this and other objects in view the invention consists in the novel steps and combinations of steps constituting the process, all as will be more fully hereinafter disclosed and particularly pointed out in the claims.

In order that the precise invention may be the more clearly understood it is said It is well known that papers of various kinds'have long since been made from materials such as those employed by us, but

it is equally well known that up to the present time, print papers derived wholly from such materials have not been commercially paper, although such short fibres have been satisfactorily used as filling materials when mixed with other and more expensive fibres.

In the, third place, the chemicals employed have been used in greater quantities and in stronger solutions than those found in our process, and they therefore have bee-n so costly as to still further increase the total Specification of Letters Patent. Patented June 6, 1922,

Application filed August 21, 1920. Serial No. 405,087.

cost of the final product. The'result has been that prior to our invention, no one has been able to commercially supply print papers and especially news print papers made wholly from straw like materials as are we;

In fact, in the case of news print paper the commercial requirements are so stringent that no one prior to us has even succeeded commercially in adding even say 10% or 20% of straw fibres to such paper.

In carrying out our invention, on the other hand, we avoid these various commercial objections and produce not only book print papers, but also news print papers, commercially, and wholly out of straw like materials, as will appear more fully hereinafter.

We accomplish these desirable results, first, by giving to the straw like materials a relatively mild first or preliminary treatment. This has the effect of producing from the straw like material a quantity of pulp making fibre of from say to 58%, or higher, of the whole, thus largely increasing the amount of pulp material from the straw.

Second, owing to this relatively mild first treatment, and the later use of kollergangs and the introduction of other features to be disclosed below, our fibres are found to'be actually longer and very much stronger than arethose which have been heretofore produced from straw like materials.

It therefore follows that the resulting paper produced by our process is of a much higher quality than that produced by prior processes. I

Third, so weak are our solutions that we only use say about 25% to 30% of the weight of the chemicals that have been heretofore employed in the making of paper from straw, and therefore, we save greatly in their cost, which very materially adds to the 'cheapness of the paper product.

Fourth, owing to the above mentioned relatively weak solutions, and mild first treatment, as well as to other features to be disclosed below, it is found that the cost of the plant, machinery, etc., is less than that for the prior processes.

Fifth, and lastly, we eliminate the usual soda recovery plant, its attendant labor and cost to run,and owing to our said first treatment, and the kollergang treatment, the bulk of the material treated is so reduced. that it is found our digestors may be say one half the capacity of the digestors heretofore employed and which treated the straw before it had been reduced in volume as it has been in our case.

This latter still further reduces the cost of the finished product.

In carrying out this process, the straw is first cut into suitable lengths of say one inch or more, and in any desired manner. It is then thoroughly screened to remove sand or other foreign substances. For the finer grades of paper, an air blast may be employed toclean the material more perfectly. The cut material is now subjected to the above mentioned first or pre-treatment by packing the same into a closed container into which a bleach and softening, or disintegrating agent is introduced.

This said bleaching and softening agent is so .chosen that the fibres are not injured or are not shortened as has been the case heretofore, and we find that we may use sulphur dioxide SO either in the form of a gas injected into the container or we may use a solution of common salt NaCl. If the gas is i used it should notbe at a pressure higher than say 2 to 10 pounds, but ordinarily we Instead of the gas, we of course may use SO in the form of a weak solution in which case, we prefer that it have a strength of not more than say one half of one per cent $0,. In practice we have found, that the gas gives the better results as it seems to penetrate the mass of material better. I

In the case of making book paper pulp, or finer grades of paper pulp, we find that it is often desirable to use as much as 5 pounds pressure of the gas. In other cases for special grades of paper, we may, of course, use higher pressuresas will readily occur to those skilled in the art.

In the case of news print paper pulp, and should a SO solution be employed, a strength of one half of one per cent S0 is desirable, as above mentioned, but in the case of book paper pulps this strength may be correspondingly increased,-or to say 1% or a little higher.

Should a sodium chloride solution be used in this first or preliminary treatment, we find that the yield of fibres will be somewhat higher even tharrwith the S0 gas or solution, and we further find that the strength of the fibre is somewhat better because the salt seems to prevent, in some way, the sugar like constituents leaving the straw or cellulose before higher temperatures are reached, with the result that the reaction taking place at said higher temperature is not so harsh or so weakening on the fibre as it would be if no salt were. used.

In the making of news print pulp we prefer to employ a solution of from 1% to2% unease of sa t in this first or preliminary treatment, and in the case of making book print paper pulp we prefer to employ a solution of from some straws have considerably more silica than others. For those straws which are relatively high in silica, of course, a harsher chemical reaction is needed, to soften their ligneous matter, than are straws which have a less silica content. Therefore, the time of treatment will depend somewhat upon the kind of straw used, and it will readily occur to those skilled in the art as to just how long this preliminary treatment should last, but under ordinary conditions, it would last from say 12 to 18 hours.

During this preliminary treatment, however, and before any steam is applied, if SO gas has been employed the material should stand, subject to the action of said gas, for say 1 to 2 hours, whereupon a sufficient quantity ofwater is added to produce a solution substantially equal in strength of S0 to that above indicated, or a solution which will ggitain say about one half of 1 per cent of After this standing, steam at a pressure sufficient, if news print paper is to be made, to produce a temperature of from say 50 to 60 C. or the temperature of the material maybe otherwise suitably raised. This temperature is maintained in the case of news print paper for a period of from say 12 to 18 hours; in the case of book print, the steam [will have a pressure suflicient to produce a temperature of from 80 to 90 (3., and it will be maintained for a period of from 18 to 24 hours. In other words, ordinarily the shorter the heating period the stronger and harder will be the resulting fibre. The longer the heating is continued the softer will be the fibre. The length of the heating period will also, of course, depend somewhat upon the character of the straw employed. Should SO gas not be used, but a solution of SO or a solution of NaCl be used in this said first, or pre-treatment, of the material, then the above mentioned heating is preferably begun immediately upon the introduction of the material into the tank, and without allowing it to stand as is the case when the gas is employed.

The result of the foregoing preliminary treatment is, as will be apparent from what has been above stated, that the ligneous matter present in the raw material is softened and to some extent dissolved, whereby the fibres of said material are not injured to any substantial extent, and whereby they may be readily liberated by the succeeding steps of the process to be disclosed below.

In addition to this, the above mentioned softening agents naturally bleach the material to a greater or less extent. Further, in the cases where the salt solutions are employed the amount of the yield of fibre is greatly increased owing to the fact that the levulosic" or other sugar like materials are left in the fibre and are not lost to the process as in the preceding cases, all as has been mentioned above. The fibres thus produced are found in practice to be abundantly strong enough for making news. print paper, and book paper. The above mentioned pre-treatment applies to all ordinary straws, and similar material, but when treating fiax straw it is preferred to handle it in all cases as if one is to make book paper pulp in the manner above disclosed. But, after this said first treatment is completed, it is preferred to wash it, and run it over kollergangs to loosen up its woody matter before it is cooked.

The other straw may be treated in this manner also, and if it is so treated it will be found to require less time in cooking and also less chemicals. On the other hand, such found to be essential in the handling of ordinary straws.

After the above mentioned preliminary treatment has been completed, the steam is cut ofi and the liquor is withdrawn from the container. This liquor may be used over several times in treating fresh batches of straw material and when so used, it becomes quite rich in potash and ammonia, and these reagents may be recovered if desired in any suitable manner. V

The straw material remaining in the tank after the liquor has been drawn off is next thoroughly washed with water and drained digestors'where .it is further cooked in the presence of a bi-sulphite pulp forming solution. As above mentioned, the total volume of the original straw has now been so reduoed' that thecapacity of these digestors need not be more than about 50% of what they would be if this preliminary treatment had not been given the straw. This said solution may contain from say to 1.1% of caustic soda NaOH', or from say to 1.1% of sodium carbonate Na CO either or both mixed with of sodium sulphate Na SO We add this bisulphite forming solution to the digestors immediately after putting inthe straw, and then raise the temperature to 125 C. in about two hours time. After'this' temperature has been reached we next add a small amount of sodium chloride NaCl which amount usually will not exceed 5%. The function of this said sodium chloride at the temperature mentioned is that of a bleaching agent.

After the above mentioned. bi-sulphate pul forming solution has been thusadded 'to e digestors, as above stated, the temperwashing and kollergang treatment is not.

after which it is transferred tosuitable upon the difference in quality of the straw I employed, or depending uponwhether or not we are to make news print paper or book print paper.

All ofthese variations will readily occur to those skilled in the art. Of course, the sooner this said solution isadded to the digestors the softer will be the final fibrous product, and vice versa. A somewhat higher temperature than that above mentioned, orv one up to say 150 C. may be employed if desired, but the higher the temperature used, the less stronger will be the resulting fibre and we have found that the ranges above given are really the best to be employed in practice because they yield the greateststrength and greatest amount of fibre.

about 4 hours in the case of news print paper, and about 6 hours in the case of book print paper, the pulp mass is blown into a wash pit' having a perforated double bottom through which the cooked liquor is withdrawn, whereupon said mass is washed and then it is transferred to a kollergang apparatus to be ground. As above intimated, it is an important feature of this invention that a kollergan is employed instead of any other type '0 beating engine for it is found to act less harshly upon the fibre, and therefore, by its use it is possible to cook the pulp up to that predetermined point at which its maximum strength of fibreis still retained, and yet, 0 1

of the pulp from the straw and it has pre- 1 I served a length of fibres and a strength of fibres which has not been attained in any prior rocesse's, in so far as we are aware.

It t erefore remains to thoroughly disintegrate the "fibre without destroying the same, and other workers inthis art, in so 1120 far as weare able to learn, have notappreciated the importance of using a kollergang type of. beating engine in connection with said mild treatment in order to preserve the 7 said strength and length of fibre just men- 1535 tioned.

0n the other hand, by combining these features we are enabled to produce print paper and book paper at a figure which heretofore has not been posslble, and therefore, 1..

we are enablbd to put such papers on the market in competition with papers produced from other sources. After leaving the kollergang the pulp is screened and bleached with chlorine or other suitable bleaching agent, in the usual manner, whereupon it is ready for the paper machine.

e have found by actual test that paper produced from straw pulp prepared in the manner above stated is strong enough to sufficiently withstand being run through fast printing presses while at the same time, as stated above, it is commercially inexpensive enough to compete elliciently with the usual news print and book print made from ground wood and chemical pulp. lVe have also found, in carrying out this process, that the cooking liquor which is withdrawn from the digestors at the end of the second step of the process may be used with good results in place of the S0 and the NaCl solutions employed in the first or preliminary step, but we prefer in most cases to employ two separate sets of solutions as has been described above.

It is obvious that those skilled in the art material from straw like substances containing ligneous matter which consists in softening said substances with a chemical softening agent; subjecting said softened substance to a kollergang treatment; subjecting the resulting mass to a digesting action in the presence of a ulp forming liquor containing mixed acid and alkali compounds; and then subjecting the mass to a second kollergang treatment, substantially as described.

' 2. The process of preparing pulp paper material from straw like substances containing ligneous matter which consists in subjecting said substances to the action of a bleaching and softening agent adapted to soften but not destroy the ligneous matter; subjecting the softened mass to a kollergang treatment; and digesting the resulting mass in the presence of a bisulphite pulp forming liquor. substantially as' described.

3. The process of preparing paper pulp material from straw like substances containing ligneous matter which consists in heating said substances in the presence of a bleaching agent adapted to soften but not destro saidligneous matter; subsequently digestlng the resulting mass. in the presence of a bi-sulphite pulp forming liquor; and injecting into said mass a solution of sodium chloride ata predetermined period of said digestion, substantially as described.

4. The process of preparing paper pulp material from straw like substances containing ligneous matter which consists in heating said substances at a predetermined temperature and for a predetermined time in the presence of a bleaching agent adapted to soften but not destroy said ligneous matter; subsequently digesting the resulting mass at a redetermined temperature for a predetermined time in the presence .of a' bisulphite pulp forming liquor; injecting into said mass at a predetermined period of said digestion asolution of sodium chloride; and mechanically grinding said mass in a kollergang type of apparatus to form a pulp, substantially as described.

5. The process of preparing paper pulp material from straw like substances containing ligneous matter which consists in heatin bl aching and softening agent of a strength too weak to injure the fibre, and to a temperature not exceeding 100 C. for a predetermined period of time not exceeding 24 hours; withdrawing said softening agent and washing the mass; subsequently digesting said mass in the presence of a pulp forming liquor at a temperature not-exceeding 160 C. fora period of time not exceeding 10 hours; injecting into said mass a solution of sodium chloride at from 2 to 5 hours after the beginning of said digesting operation; withdrawing said pulp forming liquor and washing said mass; and mechanically grinding said mass in a kollergang apparatus to form a pulp, substantially as described.

6. The process of preparing paper pulp material from straw containing ligneous matter which consists in heating said straw in the-presence of a solution of sodium chloride to bleach and soften said ligneous matter; subjecting the softened mass to a kollergang treatment and subsequently digesting the resulting mass in the presence of a pulp- .mass in the presence of a pulp forming liquor; and injecting a solution of sodium chloride into said mass at a predetermined point of said subsequent digestion, substantially as described.

In testimony whereof we alfix our signatures.

CAR-L BACHE-WIIG. JOHN BACHE-WHG.

said substances in the presence of a 

